Mechanical end face seals have long been used to seal a space between a rotating shaft and a housing. Typically, such seals include an annular collar mounted in sealing engagement upon a rotatable shaft. Attached to this collar and extending coaxially of the shaft is an elastomeric or metallic bellows which mounts a sealing washer having a radially extending sealing face. That face then engages the sealing face of a fixed washer mounted upon the housing. The sealing engagement of the two washers is effected by an axial bias which is usually exerted by a spring in the case of elastomeric bellows or by the inherent bias of a metallic bellows. That bias permits axial movement of the washer on the bellows to compensate for wear and alignment.
In operation of these seals, the bellows unit and its washer is rotated through the collar connection with the shaft. Opposing this rotation is the friction drag between the washers and fluid drag exerted by the fluid on the bellows. This rotation and the opposed drag results in the imposition of torsional deflection within the bellows. This torsional deflection tends to oppose the axial bias which effects sealing engagement. In addition, the fluid within the space may tend to seize the washers together and oppose their relative rotation. This seizing is often referred to as a "slip-stick" phenomenon.
To overcome this slip-stick phenomenon and to minimize torsional deflection on the bellows unit, the prior art has provided a mechanical interconnection between the opposite ends of the bellows. Such an interconnection is illustrated in U.S. Pat. No. 2,432,694 which issued Crane Packing Company on Dec. 16, 1947. The interconnection of that patent includes a tubular member attached to the washer and extending over an elastometric bellows. At the other end of the bellows, the tube is provided with slots engaged by lugs constrained for rotation with the shaft. That lug and slot interconnection comprises a positive drive between opposite ends of the bellows which accepts the friction drag forces precluding torsional deflection of the bellows.
In a metallic bellows seal, a similar positive drive interconnection has been used. Such a device is presently sold by Sealol, Inc., who identifies the seal as a Type 605HDL. In that device a slot and lug positive drive interconnection is positioned interiorly of the metal bellows.
Each of these prior art devices utilizes a rigid mechanical interconnection between opposite ends of the bellows units. That interconnection involves physical abutment between the lug and slot and results in a force component acting perpendicular to the axial bias maintaining the sealing washers in engagement. Further, this circumferential force component is normally maintained during opration of the seal by friction drag of the fluid and of the sealing washers. As a result, it is possible that the circumferential force component, when multiplied by the coefficient of friction, results in an axial force opposing the bias of the spring tending to effect sealing engagement of the washers. This friction force, combined with possible alignment problems and the accumulation of foreign practices in the interconnection may adversely affect axial sealing movement of the washers.